I would guess that the board inside the saucer has failed.
I say this because you tried a different power/driver board with results unchanged.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

To be sure that I understand, you've tried two power/driver boards, and more than one saucer board, and the symptom persists, right?
if that is the case, then we must look elsewhere...

...flip the MPU-to-Power/Driver board ribbon over (on both ends). Test again.
...Reseat the ASIC. Remove MPU, place on flat hard surface, press firmly on the ASIC, reinstall MPU. Test again. We removed the MPU to avoid flexing the PCB too much.
...try a different MPU. Test again.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

@jacobr_1966, if you haven't tried a different power/driver board, then the suggestions that I added can be put on the back burner.
The most likely culprit is the circuitry nicely detailed by @bakerhillpins.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Yes. Not OK.
Use the logic probe to backtrack through the circuit trying to find where the signal goes awry.
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Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/Contact ... for board repairs
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Thanks for closing the loop. It almost had to be that.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info